Nopperabo

A nopperabo reveals its true nature at the appropriately dramatic moment.

Not a terribly threatening demon, but certainly disconcerting. The nopperabo often disguises itself very successfully as a normal human being. Your friends, colleagues, even husband or wife might well be a nopperabo in hiding. But at a well-timed moment (these bakemono have a keen sense of the dramatic), a nopperabo will wipe all of the features off its face, presenting a blank and empty countenance to the viewer (and later, presumably, laughing itself silly over the reaction it gets).